Isomerization of normal paraffins



Patented Oct. 27, 1942 Kenneth C. Laughlin, Baton Rouge, La., assignorto Standard Oil Development Company, a corporation of Delaware NoDrawing.

Application D ecember Serial No. 311,112

27, ess,

I 8 Claims. (Cl. 260-676) The present invention relates to an improvedmethod for isomerizing normal straight chain paraiiin hydrocarbons, andmore specifically to :1 new class of catalyst activators for such reac-It is known that normal paraflln hydroc'arbons can. be isomerized bymeans of Friedel-Crafts catalysts, such as aluminum chloride or bromide,

zinc chloride, ferric chloride and the like, It

-is likewise known that the catalyst in almost every case requires anactivator, since without.

such activator'its activitydiminishes very rapidly. As activators,hydrogen halides, such as hydrogen chloride, have been mainly employed,

It has now been found that carbon dioxide is an excellent activator forFriedel-Crafts "type catalysts in the isomerization reaction, givingsubstantially greater yields than when a corresponding amount of ahydrogen halide is used as the activator. Carbon dioxide is, of course,a very cheap, easily handled, and readily obtainable material.Commercial isomerization proccases may therefore be conducted withlittle added cost of catalyst. activation.

The present process, in which carbon dioxide is employed as the catalystactivator, is capable of converting normal paramns, such as normalbutane, normal pent'ane, normal hexane, normal heptane and higherhomologs, into their corresponding branched'iso forms such as isobutane,isopentane, isohexane, and the like. The

- feed stock may also comprise mixtures of more than one of thesestraight chain -p, or,

if convenient, the paraflinic hydrocarbon mix-, ture may contain smallproportions of branch'ed.

tion qualities when used as motor fuels and with 1 respect to thefacility with which they may enter into further chemical reactions "toproduce al-e kylation products-whenreactedwith oieflns. In

' general, any hydrocarbon mixture predominantly of saturated straightchain hydrocarbons is suitable as a feed stock for the process hereinoutlined. A product containing substantial amounts of branched chainisomers may be separated from the reaction mediumand fractionated withinthe desired boiling range. The

constituents boiling above and below the desired rangemay then bereturned to the isomerl'zation reactor to suppress their further fonhaehalide activators.

tion orto be further isomerized to more useful products;

, The carbon dioxideactivator may be added to the feed stock, or it maybe added to the reaction chamber by independent means so as to bedistributed more'evenly through the catalyst mass. It is not necessaryto add the activator continuously, and it may be added from time to time'as the catalyst shows "deterioration. The amountof the activator varieswith the catalyst, its age, the temperature and other conditions, butordinarily the amount is from 0.5% to 5% or 10% of the feed stocktreated. I

The conditions for isomerizing with the present catalysts and activator.are much the same as those formerly employed with the-hydrogen A widetemperature range may be employed, forexample', from about to about ;400F. The higher temperatures, that is,.from' 300 to 400 F1, are preferablyemployed when the feed stocks Eare in vapor phase, and there may be somedecomposition at the same time. At the lower temperatures, for example,from to 250 E, isomerizatio'n may be effected in the liquid phase and.without side-reactions. The time of the reaction varies with otherfactors, such as temperature, the amount of catalyst, the particularcatalyst used and the particular feed stock treated. In general,however, the time of reaction may be from V: to 30 hours, and theconditions are usually adjusted so as toobtain a conversion of 50% to ata temtame and 75 to F. for pentane.

perature, for example, of to 250 F. for bu- The amount of catalyst to beused varies wide-, -ly, depending upon the particular hydrocarbon whichis to be converted, the amounts ranging from 2% to 100% by weight of thehydrocarbon material present. For the conversion of butane in thepresence of aluminum chloride, it is ad-' vantsgeous to use about 10%toabout 50%, Preferably about 15%, by weight of ahiminum chloride andabout 0.5% to about 10%,, preferably about 2%,by weicht of carbondioxide.

The reaction is preferably carried out under .liquid hase conditions.Hence'any tempera reaction products in the liquid phase under theturebelow the critical t mperature of the feed stock may be'emploved.althoush it is preferable to use the specified above. snmcientniperatmospheric pressure may be em- 7 ployed to maintain the reactants.as well as the reaction conditions obtained. In particular,

liquid phase reactions'are conducive to the pros; ductlon of ultimatehigh yields and to the carrying out of the process in a continuousmanner. It is to be understood, however, that the process is not onlyapplicable to continuous operation, but it is contemplated to carry thesame out in batch type apparatus for single batch operation. Where thereaction is carried out in the liquid phase, it has been foundadvantageous to intensively agitate the reaction mixture so thatintimate contact is established between thefeed and the catalyst. Thecatalyst may be employed as a slurry, in which case a mechanicalagitator propelled by external means is preferably inserted in thereactor. Where a batch type of Example 3 A further portion of n-butanewas treated as in Example 2, except that 2% by weight of carbon dioxidewas employed as the activator instead of the hydrogen chloride. Theresults showed a yield of 50.0% of isobutane and an n-butane concatalystis employed, it is well to employ liquid phase operation and to forcethe liquid hy drocarbon feed into the reactor under pressure throughjets of restricted internal diameter or to employ turbo mixers or somesimilar dispersion means for increasing intimacy of contact between thecatalyst and the feed. The direction of flow oi the feedstock may be upward, or downward through the catalyst bed; but where a powderedcatalyst is used, an upward flow is preferable.

In the case of batch operations, the reaction may be carried out in abomb or autoclave, preferably fitted with agitating apparatus. Incontinuous flow processes the normal paraifin is passed in vapor'orliquid condition through a reaction vessel containing the catalyst whichmay be in lump or powdered form and may be supported on a carrier suchas silica, alumina gels thereof, activated carbon, asbestos, pumice,clay and the like. The hydrocarbon feed stock may be pumped through ahorizontal chamber or vertical bed of the catalyst. The catalyst mayalso be used in finely divided form and may be passed through thereaction zone suspended in the materials being treated. The catalystsmay consist entirely of Friedel-Craits agents or may be modified by theaddition of alkali or alkaline earth halides such as potassium or sodiumchloride .or

calcium or magnesium halides.

The advantages of the present invention are illustrated by the resultsobtained in the following examples:

u Example 1 A portion 0! liquefied n-butane was agitated for 12 hours at212 F. in a closed reaction vessel in the presence of 15% by weight ofaluminum chloride. Analysis of the products showed a yield of 31.7%01isobutane in a total n-butane con-' version of 32.1%.

.. Example 2 e A portion of n-butane was treated as in Example 1, butwith the further addition of 2% by weight of hydrogen chloride as acatalyst act ivator. The results showed a yield of 42.5% ofisobutane anda total n-butane conversion of 43.1%.

version of 69.6%.

The present invention is not to be limited by any theory of the reactionmechanism or by any of the examples, which are given by way ofiilustration only, but solely by the following claims in which it isdesired to claim all novelty inherent in the invention.

I claim:

1. An improved process for isomerizing a normal parai'fln hydrocarbonwhich comprises subjecting the same to the action of a Friedel-Craitstype catalyst in the presence of a catalyst activatorcomprising about0.5% to about 10% by weight of carbon dioxide, based on the weight ofhydrocarbon present, while at a temperature from 30 to d00 F.

2. A process according to claim 1 in which the catalyst is an aluminumhalide.

3. Process according to claim 1 in which the catalyst is aluminumchloride.

4. An improved process for isomerizing a normal parafiin hydrocarbonwhich comprises subjecting the same in the liquid phase to the action ofa Friedel-Crafts type catalyst in the presence of a catalyst agitatorcomprising about 0.5% to about 10% by weight of carbon dioxide based onthe weight of hydrocarbon present, while at a temperature from about toabout 250 F.

5. Process according to claim 4 in which the catalyst is aluminumchloride. 6. An improved process for isomerizing normal butane whichcomprises subjecting the same to the action of a Friedel-Crafts typecatalyst in the presence of a catalyst activator comprising about 0.5%to about 10% by weight of carbon dioxide, based on the weight of thehydrocarbon present, while at a temperature from to 250 F. i

7. An improved process for isomerizing normal butane which comprisessubjecting the same to the action of about 10% to about 50% by weight ofaluminum chloride and about 0.5% to about 10% by weight of carbondioxide while at a temperature from 150 to 250 F.

8. An improved process for isomerising normal butane which comprisessubjecting the same to the action of about 15% by weight of aluminumchloride and 2% by weight of carbon dioxide whileat a temperature ofabout 212 F.

KENNETH C. LAUGHLIN.

